When it is appropriate to use "-ing" in a dependent clause?

Question

I tend to use sentences like these ones in my writings:

"Bob kicked the boy, injuring his left knee."

"Congress passed the brand new tariff act, increasing the prices of imported goods."

What is the specific rule for using these types of of dependent clauses (..., "verbing")? I do not know when their usage is incorrect. I feel like I use them whenever it "feels right," but I do not know when it is actually grammatically correct to use them.

Also, does the "increasing" in the second sentence refer to "Congress" or the "act"? If it is the act, then do all cases of "-ing" in the start dependent clause refer to the noun right before it?

Answer 1

Both of the two examples given

• Bob kicked the boy, injuring his left knee.

• Congress passed the brand new tariff act, increasing the prices of imported goods.

are participles formed from relative clauses. There are other kinds of participles, like absolutes. Note that the participles in these examples can be replaced by relative clauses

• Bob kicked the boy, which injured his left knee.
  (parenthetically, this sentence is ambiguous about whose knee got injured, just like the other)

• Congress passed the brand new tariff act, which increased the prices of imported goods.

In both of these cases, the antecedent of the relative pronoun is the preceding clause.
That is,
in the first sentence, Bob kicked the boy, and that's what injured the knee, and
in the second sentence, Congress passed the tariff act, and that's what increased the prices.

This type of participle formation appears to work best with non-restrictive relative clauses, btw.

Answer 2

What you're talking about isn't called a "dependent clause"; it is called an "absolute phrase." An absolute phrase joins a participle with a noun in order to modify an object outside the phrase.

It's appropriate to use an absolute phrase when you see fit, usually at the beginning or tail end of a sentence or clause. By the way, such a phrase can also be called a "participle" or a "non-finite phrase." You may hear the term "dangling participle" when such a phrase introduces a sentence improperly.

Example:

Running late for work, the car wouldn't start for John.

The text in bold is an absolute phrase that is often referred to as a "dangling participle" as it's clearly not about subject. It is not the "car" that is running late for work but "John."

An absolute phrase that introduces or trails a main clause is typically understood to relate to the subject, not the object. As such, in your example sentence, it is "Congress" (or "Congress passing") that is "increasing the price of imported goods." That is to say that "increasing the price of imported goods" modifies "Congress" and how it "passed." It can be a hazy line with absolute phrases as to whether they adjectivally modify the subject or adverbially modify the verb, so many simply say that an absolute phrase modifies the subject/verb.